Constant tension unwinding mechanism



R. LE B. BOWEN, JR

CONSTANT TENSION UNWINDING MECHANISM Nov.'11, 1958 Original Filed March 25, 1955 IN VEN TOR.

Richard LeBaron Bbwemdr.

ATTORNEYS United States PatentC CONSTANT TENSION UNWINDING MECHANISM Richard Le Baron Bowen, Jr., Barrington, R. 1.

Original application March 25, 1953, Serial No. 344,520, now Patent No. 2,781,178, dated February 12, 1957. Divided and this application November 16, 1956, Serial No. 622,651

3 Claims. (Cl. 24275.47)

This invention relates to a constant web tension unwinding mechanism and more particularly to a mechanism for maintaining a constant speed on the web tensioning mechanism through a variable speed transmission responsive to the change in brake speed which reacts to control the speed of the braking mechanism.

One of the objects ofthe present invention is to provide a constant braking force in a web unwinding mechanism.

Another object of the present invention is to provide a constant tension unwinding mechanism which will operate automatically without any attention from an operator.

Still another object is the provision of a constant tension unwinding mechanism which will inherently permit the accurate duplication of the braking force.

Other objects of the present invention will be pointed out in part and become apparent in part in the following specification and claims.

The present application is a divisional application of my co-pending application Serial No. 344,520, now Patent No. 2,781,178 dated February 12, 1957.

Uniform or constant tension is a prerequisite to uniformity of product in many web processing machines such as textiles, paper, imitation leather, printing and the like. Especially is this true in a Web coating machine where the tension in the web affects the nature and thickness of the coating material being applied to the web. Thus, when a supply roll of cloth is placed in a machine, the cloth is drawn off at a constant speed andat a given tension.

It is common practice to put a mechanical brake on the shaft of the unwinding roll of material. As the diameter of the roll decreases, the speed or linear travel of the cloth or web is maintained constant, but the speed of the unwinding roll shaft increases in proportion to the decreasing diameter of the roll. If the setting of the mechanical brake is left constant, the tension produced on the web continues to increase in proportion to the increasing speed of the unwinding roll shaft. In such a set up it is necessary to decrease the drag or setting of the mechanical brake on the roll shaft if the tension is to be maintained constant. Past devices have failed to automatically control the drag and thereby regulate the tension accurately in accordancewith the changing tension produced as the supply roll decreases in diameter.

This failure was due in part to the nature of the braking mechanism which consisted of the conventional mechanical arrangement of a brake drum and a shoe provided with a brake lining. The coeflicient of friction between the drum and shoe varied due to the heating caused by the period of operation and the unevenness of the parts and oil and dust accumulation so that the brake slipped and grabbed. There was no way of determining a brake setting for future use since the brake lining continually were down. The present invention contemplates an oil pump as a brake, the pressure of which is always determinable for future precise settings.

In the drawings:

lice

The single figure isa diagrammatic illustration of the instant invention.

Referring to the drawing, a strip of web material 11 is being withdrawn from a beam 12 by means of a drum 16, which is driven at a constant speed by, means not shown so that web 11 moves at a constant linear velocity. Beam 12 is secured to an axle 13 which has fixed to it bevel gear 14 which meshes with bevel gear 15 fixed to shaft 20 of a continuously variable speed transmission, generally indicated by reference character 17. A second shaft 21 of variable speed transmission 17 is operatively connected to a gear pump generally indicated by reference character 35 through a shaft 36, sprocket 33 fixed to shaft 36, sprocket 32 fixed to shaft 21 and chain 34 connecting sprockets 32, 33.

A reservoir 38 is provided and is operatively connected to gear pump 35 through suction line 37 and discharge line 40. A discharge valve 41 inserted in line 40 controls the power exerted by the gear pump 35. A pressure gage 42 inserted in line 40 gives a relative indication of this power.

The variable speed transmission 17 comprises a pair of parallel shafts 20 and 21 rotatably" mounted in a housing 22. Each shaft 20, 21 carries a pair of coned disks 23, 24, respectively, forming expansive V pulleys which are splined to said shafts. Coned disks 23, 24 are operatively connected through edge-active belt 25 and may be simultaneously and oppositely adjusted to provide variable speed by the simultaneous movement of levers 26a, 27a which are operatively connected to coned disks 23, 24 and pivotally separated by lever 28.

Means for moving levers 26a and 27a is provided by a governor generally indicated by reference character 120. Governor consists of a rotatable shaft 121 on which is slidably mounted flange 123a. A connector 122 fixed to shaft 121 has arms 124 pivotally mounted to connector 122, with links 125 connecting arms 124 and flange 123a. Shaft 121 is operatively connected to pump 35 by means of sprockets 130, 131 and chain 132.

A fluid motor is provided consisting of a cylinder connected to move with the lever 27a, and a piston 141 reciprocally mounted in the cylinder 140 and operatively connected to lever 26a, together with valving means 142 for controlling the relative motion of cylinder 140 and piston 141. Valve 142 is a four-way hydraulic valve with a control lever 143 operatively connected to flange 123a. Oil is supplied to control valve 142 through line 144 and the supply pressure is maintained constant by pressure reducing valve 145. Oil is returned from valve 142 to reservoir 38 through line 146.

When beam 12 unwinds, shafts 20, 21, shaft 36 and pump and governor 120 will all tend to increase in speed. As governor 120 increases in speed, arms 124 are thrown outward by centrifugal force, and flange 123a rises, moving valve lever 143 upward, introducing oil into line 147 and causing the piston to move cones 24 together and simultaneously move cones 23 apart through levers 26a, 27a, thereby restoring the pump speed to its arbitrarily set initial value. After the beam has been unwound, the transmission is at one limit. When the mechanism has stopped, flange 123a drops down, thereby leaving valve 142 in a position so that oil will be introduced to line 148. Before the next beam is installed, hand wheel 56 is turned, supplying oil to line 148 and resetting the mechanism.

It will be apparent that the braking mechanism which maintains a constant tension on the web consists of the gear pump 35 whose braking force is determined by the setting of the valve 41. Also the gear pump is utilized as a source of hydraulic pressure for the speed change mechanism 17, thus effectively reducing external means axle, a'b'ea'm carrying web on said axle, said web being unwound from said beam at a constant linear speed, a variable speed transmission provided with a first shaft, a second shaft, and speed changin'g'mechanism including a hydraulic motor, said first shaft being arranged for driving engagement with said axle, a gear pump, said second shaft being arranged for driving engagement with said gear pump, a suction line and a discharge line with a throttling valve for said pump, a hydraulic valve for controlling the action of said hydraulic motor, and means responsive to the speed of rotation of said pump for controlling said valve.

2. In a constant tension unwinding mechanism, an axle, a beam carrying Web on said axle, 'said' web being unwound from said beam at a constant'linear speed, a variable speed transmission provided with a first shaft, a second shaft, and speed changing mechanism including a hydraulic motor, said first shaft being arranged for driving engagement with said axle, a gear pump with suction line and discharge line with a" throttling valve, said second shaft having driving engagement with said gear pump, a hydraulic valve for controlling the motion of said hydraulic motor, means for controlling said valve, a governor driven from said pump, said means for controlling said valve being operatively connected to said governor.

3. In a constant Web tension unwinding mechanism, a rotatable axle providing a variable speed source of power, a beam carrying web onsaid axle, said web being un- Wound from saidbeam at a constant linear speed, a gear pump, a variable speed transmission comprising two power transmitting shafts and a speed changing mechanism, means for driving one shaft from the other, a driving connection between said axle and'one of said power transmitting shafts, a driving connection between said gear pump and the second of said power, transmitting shafts, a fluid motor coupled to said speed changing mechanism, a governor coupled to said gear pump, a four-way valve connected between said pump and said motor, and means responsive to said governor controlling said valve.

' Vandervellet a'l'. Sept 10-, 1907 Butterworth et al. Jan. 1, 1946 

